SINAMICS S120 Startdrive: Resolving ALM Enable and EP Faults

Overview

This guide walks through commissioning a SINAMICS S120 multi-axis drive line-up using SINAMICS Startdrive integrated into the TIA Portal. The reference line-up in this article is a typical Booksize configuration with an Active Interface Module (AIM), Active Line Module (ALM), Control Unit CU320-2 PN, a Double Motor Module, and two 1FK7 synchronous servomotors, controlled by a SIMATIC S7-1500 (CPU 1515-2 PN).

The most common first-day block when the line-up is first powered in the Startdrive commissioning tool is a chain of faults that trace back to two physical items: the 24 V supply at the EP terminal on the ALM, and the wiring of terminal X21 between the AIM and the ALM. The drive also has to be told that the ALM is part of the topology — this is done by activating the ALM in the project and assigning Siemens telegram 370 (or 371) to the infeed. This article documents the wiring, the telegram configuration, the Startdrive control-panel enable sequence, and the diagnostic workflow that turns a "Switching on inhibited" drive into a rotating motor.

Hardware Line-Up

The hardware used in this reference build is summarized in the table below. The S7-1500 is the PROFINET controller, the CU320-2 PN is the PROFINET device, and the ALM is the infeed. The Double Motor Module drives the two 1FK7042 axes.

System Topology and DRIVE-CLiQ Wiring

The CU320-2 PN is the DRIVE-CLiQ master for the line-up. The DRIVE-CLiQ ports are labeled X100 through X105 on the CU320-2 PN. The standard order for Booksize line-ups is:

1. CU320-2 PN port X100 → ALM port X200 (DRIVE-CLiQ port 0 on the ALM, the right-hand RJ45 socket)
2. ALM port X201 → AIM port X200
3. ALM port X202 → first axis of the Double Motor Module (X200 on the first section)
4. First section X201 → second section X200 (daisy-chain on the same Motor Module)
5. Each motor encoder is wired to its own Motor Module section via the encoder cable on X202

DRIVE-CLiQ cables must be Siemens-approved 6SL3060-4Ax or motor-side 6FX8002 cables. Mixing wrong cables is a frequent source of F0135 (encoder/DRIVE-CLiQ topology fault).

Prerequisites

• TIA Portal V17 or newer with SINAMICS Startdrive option installed (Basic is sufficient for S120 Booksize with a GSD-based CU320-2 PN; Advanced is required for the S120 safety-integrated commissioning flows).
• SINAMICS firmware on the CU320-2 PN compatible with the Startdrive version in use. The CU320-2 PN article number 6SL3040-1MA01-0AA0 ships with V5.x; check the CF card label and the Startdrive release notes before commissioning.
• PROFINET names assigned to the controller and the device (e.g. plc1515pn and cu320pn).
• 24 V control voltage present on the line-up (X124 on the CU320-2 PN, X21 on the ALM, X21 on the AIM).
• All DRIVE-CLiQ cables connected in the order shown in the topology diagram.

Step 1 — Create the Drive Topology in TIA Portal

1. Add a new S120 device in the TIA Portal project tree: Devices & networks → Add new device → Drives → SINAMICS S120.
2. Select the Control Unit CU320-2 PN (6SL3040-1MA01-0AA0). Startdrive then opens the device configuration editor.
3. Insert the AIM 6SL3100-0BE21-6AB0 at the Line infeed slot.
4. Insert the ALM 6SL3130-7TE21-6AA4 at the infeed slot. The 6SL3130-7TE21-6AA4 is the 16 kW Booksize Active Line Module — pair it with the 16 kW AIM 6SL3100-0BE21-6AB0. The article-number pair is mandatory; the ALM will not pre-charge correctly with a mismatched AIM.
5. Insert the Double Motor Module 6SL3120-2TE13-0AD0 at the next free slot. It exposes two drive objects by default.
6. Insert both 1FK7042-2AF71-1RA0-Z motors. The encoder interface on a 1FK7042 in this article number is the multi-turn absolute encoder (DRIVE-CLiQ-ready) — pick the matching encoder telegram (typically telegram 6 or telegram 86 with the 1FK7 "-Z" options).

Step 2 — Wire the EP Terminal on the ALM (X21)

The "EP" terminal is the Enable Pulses input on the line modules. On the Booksize ALM 6SL3130-7TE21-6AA4, EP is part of the X21 customer terminal block. The EP input must see a 24 V signal relative to the X21 M terminal. Without 24 V at EP the infeed stays in the "Switching on inhibited" state and the control panel will refuse to start the drive.

Step 3 — Wire the AIM to ALM X21 Enable Chain

The AIM must signal the ALM that pre-charging has finished and the line filter is healthy. The signals flow from the AIM customer terminal X21 to the ALM customer terminal X21. The minimum required wiring is:

• AIM X21.1 (RDY1) → ALM X21.1
• AIM X21.2 (RDY2) → ALM X21.2
• AIM X21.3 (M) → 24 V ground (common with the ALM M terminal)

If this link is missing, the ALM reports F07840 (line contactor / AIM enable missing) and the Startdrive control panel shows the same "Switching on inhibited" state with no apparent path to clear it.

Step 4 — Configure the Telegrams

The ALM is a PROFINET device in its own right. The standard infeed telegram for an Active Line Module is SIEMENS telegram 370 (PZD-16/16). Some applications use telegram 371 (PZD-6/6) for reduced data. The Motor Modules and 1FK7042 axes use standard telegrams 1, 2, 3, 4, 5, 6, 81, 82, 83, 84, 85, or 86 depending on the encoder option.

Set the telegrams in Startdrive as follows:

1. Select the ALM in the device view.
2. Open Properties → Telegram configuration.
3. Insert SIEMENS telegram 370 (PZD-16/16). Telegram 370 is the ALM default; do not delete it unless you have a specific reason.
4. On the PLC side, map the alarm bit ZSW1 bit 0 (ready to switch on), bit 1 (ready), bit 2 (operation enabled), and bit 3 (fault) into your control word to monitor state.
5. On each axis, set the encoder telegram to 6 (for absolute encoders) and the drive telegram to 1 (standard positioning) or 2/3/4 for additional setpoints. For the 1FK7042-2AF71-1RA0-Z with the -Z option for safety, the safety telegram is integrated into the standard telegram 6.

If you omit the ALM from the PROFINET configuration, the line-up will still power up locally but no alarms, warnings, or the Line Module control word can be exchanged cyclically. The Startdrive control panel can still be used because it is a service-level tool, but the production code will need the telegram in the slot.

Step 5 — Compile and Download to the CU320-2 PN

1. Right-click the S120 device → Compile → Hardware configuration. Resolve any topology errors before continuing.
2. Right-click → Download to device. Confirm the PROFINET name of the CU320-2 PN matches the device label.
3. When prompted, store the configuration to the CF card of the CU320-2 PN so it survives a power cycle. The dialog is RAM to ROM (Copy from RAM to ROM).

Step 6 — Use the Startdrive Control Panel to Move the Motor

1. Open the S120 device in the TIA Portal project tree.
2. Select the axis → Commissioning → Control panel.
3. Set the control-panel enable bits in this order:

4. Click Assume control priority. Startdrive takes master control of the drive. The ALM will close, the DC bus will pre-charge, the status line should turn blue or green, and the drive should reach "Operation enabled".
5. Press Start. The motor will ramp to the setpoint.
6. Press Stop, then Give up control priority before you hand the drive back to the PLC.

Verification

After the control-panel test passes, the following checks confirm the line-up is ready for the PLC program:

• ALM online diagnostics: In Startdrive, navigate to Diagnostics → Status words → Line Module. The state word ZSW1 must read 0b0000 0000 0100 1111 (Operation enabled) after the enables above are applied.
• DC bus voltage: r0070 (Control Unit) should match the line voltage × √2. For 400 V line: about 565 V DC nominal, 540–620 V acceptable.
• Encoder feedback: r0021 of each axis must increment proportionally to the rotor angle when the motor is turned by hand. If it is stuck at zero, the encoder wiring or telegram selection is wrong.
• Active faults buffer: r0945 / r0947 should be empty. Any active F code blocks further operation.
• Safety slot: If the 1FK7042-2AF71-1RA0-Z carries a safety option, the safety telegram (PROFIsafe over PROFINET) must be configured and the STO must be exercised in the acceptance test.

Troubleshooting Matrix

Drive Parameters Worth Recording at Commissioning

Once the line-up is moving, document the following parameters for the maintenance team:

Edge Cases and Field-Notes

• EP from a safety relay: if the cabinet has a safety relay, the 24 V to ALM X21.6 must come from the safety relay, not directly from the 24 V rail. A STO trip on the safety relay will drop EP, which the Startdrive control panel reports as the same "Switching on inhibited" state — but the cause is the safety chain, not the drive.
• Double Motor Module section order: on the 6SL3120-2TE13-0AD0, the first DRIVE-CLiQ port (X200) is the section physically closer to the X200 of the ALM side. If the motor does not move but the second one does, the axes have been mapped in the wrong order. Swap the axis objects in the project, or remap the DRIVE-CLiQ cables, depending on your preferred discipline.
• Power-module firmware: the ALM 6SL3130-7TE21-6AA4 was released with both V4 and V5 firmware. The CU320-2 PN 6SL3040-1MA01-0AA0 ships with V5.x; pairing a V4 ALM with a V5 CU can cause F0135 topology faults. The compatibility matrix is in the S120 Commissioning Manual, not Startdrive.
• Control priority release: if you close Startdrive without clicking "Give up control priority", the drive stays in the control-priority-held state until the next stop/restore. The PLC will see "Drive controlled by higher-level controller" as long as the flag is held.
• First motion without PLC: when the user is doing a first test without a SIMATIC program running, the control panel is the only legal way to command the drive. Do not try to drive it through PROFINET by toggling bits in TIA Portal watch tables — the control-panel handshake is required for the first power-up to take ownership.

FAQ